If you have the Ethernet Expansion, then have a look at https://wiki.onion.io/Tutorials/Reflash-The-Firmware-With-Ethernet-Expansion
The omega bootloader (uboot) has a small http server built-in, which can run and accept a new firmware over ethernet (but not WiFi) completely independently from OpenWrt - this allows to recover even seriously mis-flashed units.
This feature saved my Omega a few times back when I just had started to build my own OpenWrt images and got important details wrong in the first few attempts...
I just noticed that even when you don't have the ethernet expansion, but a second Omega with dock, you can use that to reflash, see here